published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

Typescript. Thesis (Ph. D.)--University of Hawaii, 1933. Bibliography: leaves 261-301. UHM: HAWN also has reprint: Honolulu, HI : University of Hawaii at Manoa Library, 2000. c.3

Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. Walter R. Tschinkel, Florida State University, College of Arts and Sciences, Dept. of Biological Science. Title and description from dissertation home page (viewed Sept. 24, 2004). Includes bibliographical references.

Field trials were conducted in 1988 to evaluate the effectiveness of Steinernema (=Neoaplectana) carpocapsae (Weiser) in controlling the fire ant. Infective juveniles (IJ) of the nematode were applied as drench on 235 and 422 mounds, respectively for 2-month summer and 6-week fall evaluation periods. In comparative trials, amidinohydrazone (Amdro) was applied to 249 (summer) and 65 (fall) active mounds, with 245 (summer) and 78 (fall) untreated active as controls. Nematode treatments resulted in an average of 47% control (Abbott's formula) in summer trials and 19-88% control in the fall trials, compared with 39% and 47% control, respectively with amidinohydrazone. Active mounds treated with nematodes or amidinohydrazone had significantly fewer individuals than control mounds in summer trials.

Call number: LD2668 .T4 1962 W35

Acacia ants evolved obligate protective mutualisms with acacia trees, which they defend against herbivores, food parasites and encroaching vegetation. In this mutualism, the fitness of one partner entirely depends on the other. Other ant species are parasitic on acacia trees; they nest on the tree, harvest food rewards, do not defend their own tree, and occasionally try to steal food from other trees, usually inhabited by mutualistic ants. To understand the behavioral and anatomical effects of the interaction between ants and host trees, I integrated brain anatomy, morphology and field experiments to study parasitic and mutualistic species of Pseudomyrmex ants associated with acacia trees. In Chapter 1, I describe a previously unknown behavior of stealing food from other ant-defended acacia trees in the parasitic acacia ant P. nigropilosus, and I evaluate four strategies that may allow parasitic ants to overcome the usually effective defenses of the robbed mutualistic ants protecting a host tree. In Chapter 2, I study how colony size correlates with the degree of division of labor and brain anatomy of workers, focusing on a species of acacia ant lacking morphological castes among workers, P. spinicola. In Chapter 3, I study acacia-ant behavior of killing vegetation encroaching on a host tree. I document the interspecific differences among acacia ants in the size of the area around the host tree that workers clear from encroaching vegetation. I further test for interspecific variation in pruning behavior, and whether mandibular force correlate with worker pruning decisions. In Chapter 4, I test whether ant species that routinely leave the host tree to forage or to prune encroaching vegetation are better at orienting themselves when returning to their host tree, compared to ant species that rarely leave their host tree. This dissertation documents how the obligate protective mutualism of an ant with a tree has consequences for division of labor, navigational skills, behavioral specializations, head shape and brain anatomy of ant workers. / text

Ants are key players in ecosystem function, especially in the tropics, yet little is known about the diversity and behavior of tropical ant communities. In a lowland wet forest of La Selva, Costa Rica ants are the primary predators of over a third of the sizes of bird-dispersed seeds. Dominated by the tribes Attini, Pheidolini and Solenopsidini, 35-38 species of ant preyed on seeds or seed baits. This is the most diverse granivorous ant community yet recorded, with the high diversity associated with higher population densities, smaller colony sizes and smaller body sizes than North American granivorous ant communities. The size of a frugivore dropping is isometric with the size of the bird producing it, and decreases with rain. Ant predation on these droppings was highly variable in time and space. Discovery and recruitment to droppings increased with dropping size as predicted by simple models. However, partial predation of large droppings produced the highest seed mortality at intermediate-size droppings. Seeds were found in 29% of meter-square samples of ant nests, suggesting seed rain was not highly localized. Small droppings were used by the greatest variety of species--this corresponded to observations of ant aggression at the largest droppings. Niche breadth increased with body size for both seed size and microclimate. Large ants foraged in a greater range of Vapor Pressure Deficits than small ants, as predicted by the law of surface area to volume. Large ants also took a greater variety of seed sizes than small ants, aided through intraspecific size matching in the large species (mostly attines). The tendency for small ant species to have niches nested within those of large ant species highlights the need to understand how body size and colony size influence interactions in ant communities.

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